Currently, many anti-tumor agents such as antimetabolites (Ara-C, methotrexate, or the like), plant alkaloids (vincristine), alkylating agents (endoxan), anticancer antibiotics (adriamycin, idarubicin mitomycin, or the like), and platinum agents (cisplatin) which are used in malignant tumors are known. Among these, examples of polypeptide agents include human interferon-γ polypeptides (for example, refer to PTL 1) or polypeptides (for example, refer to PTL 2) formed of a human tumor necrosis factor (TNF) or a part of a converter of the human tumor necrosis factor. Particularly, in recent years, remarkable progress in molecular-targeted therapeutic agents (imatinib or the like) with high tumor specificity, monoclonal antibodies (rituximab or the like), or the like has been recognized and the therapeutic effects thereof have also become high. However, the spectrum of an anti-tumor effect of the anti-tumor agent such as imatinib is narrow and a drug should be selected for each tumor. In addition, there is also a problem of drug resistance. For this reason, a more effective drug of which the spectrum of an anti-tumor effect is wide has been expected in the medical field.
In contrast, a human LIX1L gene (Lix1 homolog-like; hereinafter, in some cases, also referred to as hLIX1L) is a structural gene that encodes LIX1L protein consisting of 337 amino acids. Although the molecular biological role of LIX1L is still unclear, it has been reported that the expression level thereof varies depending on the type of cell. For example, in PTL 3, there is a report that a LIX1L gene is one of 266 kinds of genes in which there is a statistically significant difference (P<1.0×10−5) in the expression level, in a cell which is sensitive to a compound, which is an AhR agonist and is activated by CYP1A1, and in a cell which is not sensitive to the compound. In addition, in PTL 4, there is an example of a LIX1L gene as one gene out of many gene groups in which the expression level increases or decreases in accordance with allergies.